Toner, developer, image forming apparatus, and image forming method

Abstract

A toner includes a binder resin including a copolymer resin containing structural units derived from crystalline and non-crystalline resins, respectively. Spin-spin relaxation time (t50) of the toner at 50° C. measured by pulse NMR is ≦0.05 msec., spin-spin relaxation time (t130) at 130° C. when warmed from 50° C. to 130° C. is >15 msec., and spin-spin relaxation time (t′70) at 70° C. when cooled from 130° C. to 70° C. is ≦1.00 msec. A binarized image obtained by binarizing a phase image of the toner observed by a tapping mode AFM based on intermediate value between maximum and minimum phase difference values in the phase image includes first phase difference images constituted by large phase-difference portions and a second phase difference image constituted by a small phase-difference portion. The first phase difference images are dispersed in the second phase difference image. The dispersion diameter of the first phase difference images is 150 nm or less.

The invention claimed is: 
     
       1. A toner, comprising:
 a binder resin, comprising 
 a copolymer resin comprising a structural unit derived from a crystalline polyester resin and a structural unit derived from a non-crystalline polyester resin, such that a molar ratio of a crystalline segment to a non-crystalline segment in the copolymer resin is from 10/90 to 40/60, where the crystalline segment comprises the structural unit derived from the crystalline polyester resin and the non-crystalline segment comprises the structural unit derived from the non-crystalline polyester resin, 
 wherein a spin-spin relaxation time (t50) of the toner at 50° C. measured by pulse NMR is 0.05 msec or shorter, a spin-spin relaxation time (t130) of the toner at 130° C. when warmed from 50° C. to 130° C. is 15 msec or longer, and a spin-spin relaxation time (t′70) of the toner at 70° C. when cooled from 130° C. to 70° C. is 1.00 msec or shorter, and 
 a binarized image of the toner, which is obtained by binarizing a phase image of the toner observed by a tapping mode AFM based on an intermediate value between a maximum value and a minimum value of phase difference in the phase image, includes first phase difference images constituted by portions having a large phase difference, and a second phase difference image constituted by a portion having a small phase difference, such that the first phase difference images are dispersed in the second phase difference image, and that a dispersion diameter of the first phase difference images is 150 nm or less. 
 
     
     
       2. The toner according to  claim 1 , wherein:
 the crystalline polyester resin comprises a dihydric aliphatic alcohol component and a divalent aliphatic carboxylic acid component as constituent components; and 
 the non-crystalline polyester resin comprises a dihydric aliphatic alcohol component and a polyvalent aromatic carboxylic acid component as constituent components. 
 
     
     
       3. The toner according to  claim 1 , wherein the first phase difference images have a dispersion diameter of from 10 nm to 100 nm. 
     
     
       4. The toner according to  claim 1 , wherein the copolymer resin is produced by reacting the crystalline polyester resin, the non-crystalline polyester resin, and an elongating agent comprising two or more of an isocyanate group, an epoxy group, and a carbodiimide group. 
     
     
       5. The toner according to  claim 1 , wherein the binder resin further comprises a second crystalline resin. 
     
     
       6. A developer, comprising:
 the toner of  claim 1 . 
 
     
     
       7. An image forming apparatus, comprising:
 an electrostatic latent image bearing member; 
 an electrostatic latent image forming unit configured to form an electrostatic latent image on the electrostatic latent image bearing member; and 
 a developing unit comprising the toner of  claim 1 , and is configured to develop the electrostatic latent image formed on the electrostatic latent image bearing member to form a visible image. 
 
     
     
       8. An image forming method, comprising:
 developing an electrostatic latent image formed on an electrostatic latent image bearing member with the toner of  claim 1  to form a visible image; 
 transferring the visible image to a recording medium; and 
 fixing the visible image transferred to the recording medium thereon.